Archyne for VS Code

Draw Mermaid diagrams on a canvas, in the editor that already has the file open — a .mmd file, or a ```mermaid block inside the Markdown you were already writing. The file stays ordinary: VS Code owns it, so the dirty dot, undo, save and the diff against HEAD all behave exactly as they do for the text.

Nothing leaves your machine. The editor is bundled — no service, no account, no network call of its own.

Getting started

Open a .mmd or .mermaid file, then run Archyne: Open on the canvas from the command palette, or use Reopen Editor With… and pick Archyne.

The text editor stays the default. The canvas is a second way to look at the file, not a replacement for reading it — and edits go both ways: move a node and the file is rewritten, type in a text editor open on the same file and the canvas redraws.

Seven diagram families can be edited on the canvas: flowchart, sequence, class, state, entity-relationship, C4 and architecture-beta. Anything else Mermaid can draw opens read-only, rendered rather than refused.

Mermaid inside Markdown

Most Mermaid is not in a .mmd file — it is a fenced block in a README, an ADR or a page under docs/. Those get an Open on canvas action above the fence:

```mermaid
flowchart TD
  api --> db
```

Click it and the canvas opens beside the file, on that block alone. What you draw is written back into the same fence, with the rest of the document — and the block's own indentation, if it sits inside a list item — left alone. The command palette has the same thing as Archyne: Open the Mermaid block at the cursor on the canvas, which is also how to reach it without a mouse.

Tilde fences and longer backtick fences work. A ```mermaid block nested inside a wider fence is example text about Mermaid rather than Mermaid, and is skipped, as is a block with no closing fence. Set archyne.codeLens.enabled to false to turn the action off.

If the block is deleted while its canvas is open, Archyne stops writing to the file and says so once, rather than guessing at a neighbouring block. The panel stays open so you can copy your work out of it.

Saving is VS Code's

While VS Code owns the file, Archyne stands aside from it: no Save, no Save as…, no Open, no Reload from disk, no New diagram, and no document tabs of its own. Ctrl+S and Ctrl+O reach VS Code rather than being intercepted, and nothing is kept in the extension's own storage.

Everything that edits the diagram is still here — templates, import, export, the canvas, the Mermaid source panel — because VS Code saves whatever comes out of them.

Known limitations

• Archyne is alpha, and this carries it. The accessibility report is self-assessed, the translations have not been reviewed by native speakers, and there has been no independent security review.
• The canvas's undo history is its own. Closing the editor tab and reopening it re-reads the file, as it should, but the canvas does not restore its undo stack — that one is not VS Code's. Ctrl+Z in the text editor is unaffected.

Elsewhere

Archyne also runs as a web app, a desktop application, npx archyne, and an MCP server for agents. Source, issues and the full changelog are at github.com/dariodd/archyne.

MIT licensed.